Production printing systems typically use a number of ink jet heads for imprinting onto continuous form media (e.g., large rolls of paper). For example, in a CMYK (Cyan, Magenta, Yellow, and Key (e.g., black) ink jet printer, 4 print heads may be used; one for each color. An ink jet head is an array of nozzles that eject ink drops at high speed onto a media to generate a printed output. The nozzles are fabricated in the print head to represent a pel or pixel of the output. For example, in a 1200 DPI (dots per inch) print head that is 20 inches wide, 24,000 nozzles are used to generate a line of pels on the media, also known as a “scan line”. A data buffer for the print head stores pel data for each nozzle of the print head. Pel data is typically multiple bits per pel that are used to vary the ink output of a nozzle over a range. In the 1200 DPI print head example, the buffer may store 24,000 pels of data, one pel per nozzle. As the media advances, the print head ejects ink based on the pel data in the buffer to render each line in the printed output. As the media moves, new pel data for the print head is loaded into the buffer, and pel data is printed by the print head. This process continues to generate the output.
In production printing systems, controlling the lateral movement of the media with respect to a print head is desired to ensure that print margins are maintained and that images appear straight and centered within the media. Due to the mechanical complexity in routing the paper through the printing system, some type of lateral movement of the media with respect to the print head is always present. This movement is oscillatory in nature and may be as much as +/−1 mm with a period of a few meters. The movement of the media poses a problem, as it alters the print margins and the location of printed regions with respect to the edges of the media.
It thus remains a problem to compensate for the lateral motion of the media with respect to the print head in order to more accurately generate printed documents.